Comprehensively mapped for the first time, Great Lakes wetlands, like this one in
Cheboygan, Mich., provide important habitat and resources.

Fluorescent bands of color outline the Great Lakes on a new, comprehensive map of
the region’s coastal wetlands. This publicly available map is the first of its kind on such a broad scale — and the only one to trump political boundaries. Both Canadian
and US wetlands are shown along more than 10,000 miles of shoreline.

Laura Bourgeau-Chavez, MTRI research scientist and the project leader for the wetlands
map, says establishing standard methods was crucial. “This is the first map to span
the entire basin, and it’s important to have a consistent map over the entire area,”
she says, explaining that inconsistencies impact data analysis and implementation
of management strategies “if you don’t know the accuracy of the map or how it’s changing
from one place to another.”

Wetlands Changing

And wetlands are dynamic systems — there is a lot of change naturally happening, although
most comes from humans. “We’ve lost more than 50 percent of coastal wetlands in the
Great Lakes over the past century,” Bourgeau-Chavez says. “The wetlands are very important
because they serve as filtration as well as habitat — and a lot of them are being
degraded.”

Managing the remaining wetlands requires a 30,000-foot view.

Although it’s more like a million-foot view, since the satellites used to map the
wetlands orbit at about 200 miles above the earth’s surface. Satellite imagery and
measurements are techniques collectively called remote sensing.

“It’s studying something from a distance,” Bourgeau-Chavez says, adding that a lot
of ground can be covered. “An example people are familiar with is using Google Earth,
that’s remote sensing.”

Bourgeau-Chavez and her team specifically used three-season PALSAR remote sensing data, which is a 23 cm wavelength Synthetic Aperture Radar (SAR). SAR satellites are useful
for measuring wetlands because the technique can distinguish flooded ground, vegetation’s
vertical structure, soil moisture and the total mass of vegetation. All these wetland
features can vary greatly between seasons, so the satellite data was collected in
spring, summer and fall.

Remote sensing can’t replace field reports, however. Mixed readings — overlapping
pixels in the data — blurred some of the map’s boundaries, making vegetation type
difficult to distinguish. With such an extensive map, field checking every point was
impossible, but “we tried to get as many as possible within each mapped area,” Bourgeau-Chavez
says. To do so, her team visited more than 1,400 separate field sites.

Invasive Species

Visiting the sites allowed the researchers to double check the predominant vegetation,
which is important for tracking invasive species like Phragmites (common reed) and cattails. Following Phragmites monocultures in the Great Lakes initiated the wetlands mapping.

In addition to keeping tabs on invasives, classifying different kinds of wetlands
is a crucial map feature. For example, peatlands are an important wetland to separate
out. The bogs are sometimes mined for peat, and they store large amounts of carbon.

“An emergent wetland that doesn’t have any, or very little, peat at the surface is
very different from a peatland with peat that is meters deep,” Bourgeau-Chavez says.

Peatlands and other wetlands can be connected to water bodies even if they’re not
directly on one of the lakeshores. To account for this water connectivity, the researchers
mapped 6.2 miles inland, creating the map’s brightly colored band following the coast.
Mapping inland also allowed the mapping team to see “the adjacent land that affects
the quality of the water going into those wetlands,” Bourgeau-Chavez explains.

There are a lot of other factors considered in land use management in addition to
monitoring urban and agriculture proximity, invasive species and different wetland
types. A variety of uses were built into the mapping interface, and viewers can also request data by clicking a button below the map legend.

So far, Bourgeau-Chavez says people have downloaded the data for everything from road
building in Michigan to Lake Erie coastal restoration to research on grass carp.

“This Great Lakes Restoration Initiative project -- made possible by an EPA grant
– produced updated coastal wetlands maps that will help the United States and Canada
better target efforts to restore critical habitats and to protect native aquatic and
terrestrial species in the Great Lakes Basin,” said Susan Hedman, EPA’s Region 5 Administrator/Great
Lakes National Program Manager. Bourgeau-Chavez says “We have a whole list of people,
both from Canada and the US, downloading the data,” and adds that as the first comprehensive
wetlands map of the Great Lakes, it has many applications.

She also notes the map is part of a greater initiative to develop better science resources
for the Great Lakes. While large, the map is only part of the picture — a picture
that will keep expanding with more detailed satellite imagery and updates as the region’s
wetlands change.

Michigan Technological University is a public research university, home to more than
7,000 students from 60 countries. Founded in 1885, the University offers more than
120 undergraduate and graduate degree programs in science and technology, engineering,
forestry, business and economics, health professions, humanities, mathematics, and
social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway
and is just a few miles from Lake Superior.